1. Field of the Invention
The present invention relates to a targeting fixture that provides for three degrees of freedom with respect to a grid template. More particularly, the present invention relates to a targeting fixture for providing a seed-implanting instrument in a particular x,y,z location with respect to a grid template, to thereby apply the seeds in order to treat a patient.
2. Description of the Related Art
For treating prostate cancer, radioactive seeds are provided to various locations within a patient""s prostate gland. Typically, a base unit which includes an ultrasound unit is used to determine the exact location of the patient""s prostate gland with respect to the base unit. The ultrasound unit includes a probe, which is inserted into the patient""s rectum while the patient is lying on his back. A grid template is mounted onto a stepper unit that is itself mounted onto an angular adjustment unit (or xe2x80x9cbase unitxe2x80x9d), whereby the grid template includes a plurality of rows and columns of holes in which a needle can be inserted. Typically, the grid template includes 13 by 13 matrix of needle holes, where adjacent holes on a row or column are 5 mm apart. Every other row is labeled with a number, and every other column is labeled with an alphabetic character. There is a direct relation between the centerline axis of the ultrasound probe and the position of the holes of the grid template. The base unit/stepper unit structure is capable of moving either in a radial direction or in an inwards or outwards direction with respect to the patient.
By using the ultrasound unit, a precise position of the proximal and distal positions of the prostate gland can be determined and recorded. The distal position of the prostate gland is also called the xe2x80x9czero retraction pointxe2x80x9d. Once that information is recorded, a pre-plan can be determined by a doctor, where the pre-plan corresponds to a plan for injecting seeds into particular locations within the patient""s prostate gland. Such treatment is generally started by placing the needle at the zero retraction point, and then applying seeds with respect to that reference point. After the pre-plan has been determined, a needle is provided through a hole on the grid template, and then inserted into a region within the patient""s body in which the prostate gland is located.
For a conventional seed implantation device, a needle is first placed into a particular hole of the grid template, and then the seed implantation device is held in place by a doctor and attached to the needle. The seed implantation device is then used to inject one or more seeds into the patient""s body through the needle. When finished with that hole, the seed implantation device is deattached from the needle, and placed aside. Then, the needle is removed from the grid template, and a new needle is positioned at another hole of the grid template, according to the specific pre-plan for treating the patient""s prostate gland. One such conventional seed implantation device is called a MICK applicator, and requires the operator to physically reposition the MICK applicator back onto a new needle positioned onto the grid template.
With such a scheme, the instrument may become unsterile when it is placed aside between replacements of needles. Also, there may exist inaccuracies due to the doctor not placing the instrument at the correct seed-implanting position with respect to the grid template (z-axis position) due to the instrument being somewhat unwieldy and hard to hold in place.
One object of the present invention is to provide a mounting device that mounts to a mounting structure on which a grid template is also mounted, and that allows a seed-implanting instrument to be accurately placed into a proper x,y,z location with respect to the grid template, for implanting seeds into a patient""s body.
Another object of the present invention is to provide a mounting device for a grid template that properly positions an instrument so that it is lined up orthogonally with respect to a front face of the grid template, no matter what x,y,z position the mounting device is currently positioned.